Stent fabrication method

ABSTRACT

A stent and a method for fabricating the stent are disclosed. The stent has an originally flat pattern and connection points where the sides of the flat pattern are joined. The method includes the steps of a) cutting a stent pattern into a flat piece of metal thereby to produce a metal pattern, b) deforming the metal pattern so as to cause two opposing sides to meet, and c) joining the two opposing sides at least at one point. Substantially no portion of the stent projects into the lumen of the stent when the stent is expanded against the internal wall of a blood vessel.

FIELD OF THE INVENTION

[0001] The present invention relates generally to methods of fabricatingstents.

BACKGROUND OF THE INVENTION

[0002] Stents are known in the art. They are typically formed of acylindrical metal mesh which can expand when pressure is internallyapplied. Alternatively, they can be formed of wire wrapped into acylindrical shape.

[0003] As described in U.S. Pat. No. 4,776,337 to Palmaz, thecylindrical metal mesh shape is produced by laser cutting a thin walledmetal tube. The laser cuts away all but the lines and curves of themesh.

[0004] The method of U.S. Pat. No. '337 is applicable for relativelylarge mesh shapes and for meshes whose lines are relatively wide.However, for more delicate and/or intricate shapes, the spot size of thelaser is too large.

SUMMARY OF THE PRESENT INVENTION

[0005] It is, therefore, an object of the present invention to provide astent fabrication method which can produce stents with relativelyintricate and/or delicate designs.

[0006] The method involves first creating a flat version of the desiredstent pattern from a piece of thin sheet metal. The flat pattern can beproduced through any suitable technique, such as etching the design intothe sheet metal, or by cutting with a very fine laser, should one becomecommercially available or by any other technique.

[0007] Once the sheet metal has been cut, it is deformed so as to causeits edges to meet. To create a cylindrical stent from a flat, roughlyrectangular metal pattern, the flat metal is rolled until the edgesmeet. The locations where edges meet are joined together, such as byspot welding. Afterwards, the stent is polished, either mechanically orelectrochemically.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention will be understood and appreciated morefully from the following detailed description taken in conjunction withthe drawings in which:

[0009]FIG. 1 is a flow chart illustration of the stent fabricationmethod of the present invention;

[0010]FIGS. 2A, 2B and 2C are illustrations of three alternative stentpatterns to be etched, in accordance with the method of FIG. 1, into aflat sheet of metal;

[0011]FIG. 3 is an isometric illustration of a stent being deformed,useful in understanding the method of FIG. 1;

[0012]FIG. 4 is an isometric illustration of a stent formed from themethod of FIG. 1;

[0013]FIGS. 5A and 5B are side and top view illustrations, respectively,of one connection location of the stent of FIG. 4;

[0014]FIG. 6 is a side view illustration of one connection location ofthe stent of FIG. 4 which is connected in a nail-like manner;

[0015]FIG. 7 shows a piece of sheet metal with a plurality of patternsmade in accordance with the invention;

[0016]FIG. 8 shows a detailed view of one of the patterns shown in FIG.7;

[0017]FIG. 9 shows a detailed view of a pair of engagement troughs shownin FIG. 8;

[0018]FIG. 10 shows a detailed view of a pair of engaging protrusionsshown in FIG. 8;

[0019]FIG. 11 shows the engagement troughs and engagement protrusions ofFIGS. 9 and 10 in the engaged position;

[0020]FIG. 12 shows a welding run practiced in accordance with theinvention;

[0021]FIG. 13 is a detailed view of the welding run shown in FIG. 12;

[0022]FIG. 14 is a detailed view of a cell of a stent made in accordancewith this invention;

[0023]FIG. 15 is a detailed view of a cell made in accordance with thisinvention;

[0024]FIG. 16 shows a cell of a stent made in accordance with thisinvention;

[0025]FIG. 17 is an enlarged view of the cell shown in FIG. 16;

[0026]FIG. 18 is a cross-sectional view of a longitudinal member of astent constructed in accordance with this invention;

[0027]FIG. 19 is a cross-sectional view of a stent constructed inaccordance with this invention;

[0028]FIG. 20 is a perspective view of a stent constructed in accordancewith this invention;

[0029]FIG. 21 is a cross-sectional front view of an unexpanded stentmade in accordance with the invention;

[0030]FIG. 22 is a cross-sectional front view of the stent shown in FIG.21 after it has been expanded;

[0031]FIG. 23 is a cross-sectional front view of an unexpanded stentmade by cutting a pattern in a tube; and

[0032]FIG. 24 is a cross-sectional front view of the stent shown in FIG.23 after expansion.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0033] Reference is now made to FIG. 1, which illustrates the stentfabrication method of the present invention and to FIGS. 2A, 2B, 2C, 3and 4 which are useful in understanding the method of FIG. 1.

[0034] In the stent fabrication method of the present invention, a stentdesigner first prepares a drawing of the desired stent pattern in a flatformat (step 10).

[0035]FIGS. 2A, 2B and 2C illustrate three exemplary stent patterndesigns. The pattern of FIG. 2A has two types of sections 20 and 22.Each section 20 has two opposing periodic patterns and each section 22has a plurality of connecting lines 24. The pattern of FIG. 2A can beformed of any size; a preferable size is to have each section 20 bebetween 1 and 6 mm wide and each section 22 have connecting lines 24 of1-6 mm long. At such sizes, the pattern of FIG. 2A cannot be cut using alaser cutting system.

[0036] The pattern of FIG. 2B is similar to that of FIG. 2A in that italso has sections 20 of opposing periodic patterns. The pattern of FIG.2B also has connecting sections, labeled 30, which have a Z shape.

[0037] The pattern of FIG. 2C has no connecting sections. Instead, ithas a series of alternating patterns, labeled 32 and 34.

[0038] The patterns of FIGS. 2A, 2B and 2C optionally also have aplurality of small protrusions 38 which are useful in forming the stent,as described hereinbelow

[0039] Returning to FIG. 1, in step 12, the stent pattern is cut into aflat piece of metal (“sheet metal”). The metal can be any type ofbiocompatible material, such as stainless steel, or a material which isplated with a biocompatible material. The cutting operation can beimplemented in any of a number of ways, such as by etching, or bycutting with a fine cutting tool, or by cutting with a very fine laser,should one become commercially available.

[0040] If step 12 is implemented with etching, then, the process isdesigned to cut through the sheet metal. This process is known; however,for the purposes of completeness, it will be briefly describedhereinbelow.

[0041] The drawing of the pattern is reduced and printed onto atransparent film. Since it is desired to cut completely through themetal, the drawing is printed onto two films which are joined togetherin a few places along their edges. The sheet metal is covered, on bothsides, with a layer of photoresist and placed between the twotransparent, printed films. The structure is illuminated on both sideswhich causes the portions of the photoresist which receive the light(which are all the empty spaces in the pattern, such as spaces 26 ofFIG. 2A) to change properties.

[0042] The sheet metal is placed into acid which eats away thoseportions of the photoresist which changes properties. The sheet metal isthen placed into an etching solution which etches away all material onwhich there is no photoresist-removing solution which removes thephotoresist, leaving the metal having the desired stent pattern.

[0043] In step 14, the metal pattern is deformed so as to cause its longsides (labeled 28 in FIGS. 2A, 2B and 2C) to meet each other. FIG. 3illustrates the deformation process. For cylindrical stents, thedeformation process is a rolling process, as shown.

[0044] If the protrusions 38 have been produced, after deformation ofthe metal pattern, the protrusions 38 protrude over the edge 28 to whichthey are not attached. This is illustrated in FIG. 5A.

[0045] In step 16, the edges 28 are joined together by any suitableprocess, such as spot welding. If the protrusions 38 were made, theprotrusions 38 are joined to the opposite edge 28, either by welding,adhesive or, as illustrated in FIG. 6, with a nail-like element 40. FIG.5B illustrates the connection of the protrusion to the opposite edge 28.Since protrusion 38 is typically designed to extend the width of oneloop 39, the pattern in approximately preserved. This is seen in FIG.5B.

[0046] Alternatively, the edges 28 can be brought together and joined inthe appropriate places.

[0047]FIG. 4 illustrates a stent 31 formed by the process of steps 10-16for the pattern of FIG. 2A. It is noted that such a stent has connectionpoints 32 formed by the joining of the points 30.

[0048] Finally, the stent 31 is polished to remove any excess materialnot properly removed by the cutting process (step 12). The polishing canbe performed mechanically, by rubbing a polishing stick having diamonddust on its outside inside the stent 31. Alternatively, anelectropolishing unit can be utilized.

[0049]FIG. 7 shows an alternative embodiment of the invention in which aplurality of patterns 120 are etched and cut into the sheet metal 121 aspreviously discussed. FIG. 8 is an enlarged view of one of the pluralityof patterns 120 shown in FIG. 7.

[0050]FIG. 9 is an enlarged view of one pair 127 of the plurality ofengagement troughs 128 and 129 shown in FIG. 8. FIG. 10 is an enlargedview of one pair 130 of the plurality of engagement protrusions 131 and132 shown in FIG. 8. The sheet metal 121 and each of the patterns 120 isprovided with a plurality of alignment apertures 122 and 122′ adapted toreceive sprockets. (not shown) for precisely moving and maintaining theprecise alignment of the sheet metal 121 and the patterns 120 during thevarious stages of manufacturing. Each pattern 120 has a first long side123 and a second long side 124, a first short side 125, and a secondshort side 126. The first long side 123 is provided with a plurality ofpairs 127, 127′ and 127″ of engagement troughs 128 and 129 (shown ingreater detail in FIG. 9). Each pair 127, 127′ and 127″ of engagementtroughs has a first engagement trough 128 and a second engagement trough129. The second long side 124 is provided with a plurality of pairs 130,130′ and 130″ of engagement protrusions (shown in greater detail in FIG.10). Each pair 130, 130′ and 130″ of engagement protrusions is providedwith a first engagement protrusion 131 and a second engagementprotrusion 132. The pairs of engagement protrusions 130, 130′ and 130″are disposed substantially opposite the pairs of engagement troughs 127,127′ and 127″.

[0051] The engagement troughs 128 and 129 are disposed and adapted toreceive and engage the engagement protrusions 131 and 132 so that thealignment of the stent is maintained when the pattern 120 is deformedand the flat sheet metal is rolled so that the first long side 123 andthe second long side 124 meet each other to form a tube as shown inFIGS. 19 and 20.

[0052] A bridge 133 of material is disposed between each pair 127, 127′and 127″ of engagement troughs 128 and 129. This bridge 133 impartsadditional stability and facilitates alignment during manufacturing andimparts additional strength to the welds of the finished stent asdiscussed below.

[0053] After the sheet has been rolled into a tubular stent and theengagement troughs 128 and 129 have received the engagement protrusions131 and 132, means (not shown) are utilized to maintain the alignmentand the bridge 133 is cut to leave two substantially equal parts. Thebridge 133 may be cut in a variety of ways well known to those skilledin the art, however, in a preferred embodiment, a laser is utilized.Engagement trough 128 is welded to engagement protrusion 131 andengagement trough 129 is welded to engagement protrusion 132 as shown inFIGS. 12 and 13. This may be accomplished in a variety of ways wellknown to those skilled in the art, however, in a preferred embodiment aplurality of spot welds are utilized. In an especially preferredembodiment, about five spot welds are used in each weld run as shown inFIGS. 12 and 13. The heat produced by the welding melts the cut bridge133 material and the material is drawn towards the engagement trough 128or 129 to which the material is attached and is drawn into the weldedarea between the engagement trough and the engagement protrusion wherethe additional bridge material becomes part of and imparts additionalstrength to the weld. The stent may then be finished as previouslydiscussed.

[0054]FIG. 13 is an enlarged view of the welded area shown in FIG. 12.In a preferred embodiment, the weld run is offset from the point wherethe engagement trough and the engagement protrusion contact each other.In an especially preferred embodiment, the weld run is offset about 0.01mm.

[0055]FIG. 14 is a detailed view of the pattern shown in FIG. 8. Asshown in FIGS. 14 and 20, Applicants' invention can also be described asan expandable stent defining a longitudinal aperture 80 having alongitudinal axis or extension 79 and a circumferential axis orextension 105, including a plurality of flexible connected cells 50 witheach of the flexible cells 50 having a first longitudinal end 77 and asecond longitudinal end 78. Each cell 50 also is provided with a firstlongitudinal apex 100 disposed at the first longitudinal end 77 and asecond longitudinal apex 104 disposed at the second longitudinal end 78.Each cell 50 also includes a first member 51 having a longitudinalcomponent having a first end 52 and a second end 53; a second member 54having a longitudinal component having a first end 55 and a second end56; a third member 57 having a longitudinal component having a first end58 and a second end 59; and a fourth member 60 having a longitudinalcomponent having a first end 61 and a second end 62. The stent alsoincludes a first loop 63 defining a first angle 64 disposed between thefirst end 52 of the first member 51 and the first end 55 of the secondmember 54. A second loop 65 defining a second angle 66 is disposedbetween the second end 59 of the third member 57 and the second end 62of the fourth member 60 and is disposed generally opposite to the firstloop 63. A first flexible compensating member or flexible link 67 havinga first end 68 and a second end 69 is disposed between the first member51 and the third member 57 with the first end 68 of the first flexiblecompensating member or flexible link 67 communicating with the secondend 53 of the first member 51 and the second end 69 of the firstflexible compensating member or flexible link 67 communicating with thefirst end 58 of the third member 57. The first end 68 and the second end69 are disposed a variable longitudinal distance 70 from each other. Asecond flexible compensating member 71 having a first end 72 and asecond end 73 is disposed between the second member 54 and the fourthmember 60. The first end 72 of the second flexible compensating memberor flexible link 71 communicates with the second end 56 of the secondmember 54 and the second end 73 of the second flexible compensatingmember or flexible link 71 communicates with the first end 61 of thefourth member 60. The first end 72 and the second end 73 are disposed avariable longitudinal distance 74 from each other. In a preferredembodiment, the first and second flexible compensating member orflexible links 67 and 71 are arcuate. The first and second flexiblecompensating member or flexible links 67 and 71 are differentiallyextendable or compressible when the stent is bent in a curved directionaway from the longitudinal axis 79 of the aperture 80. (Shown in FIG.20.) The first member 51, second member 54, third member 57, and fourthmember 60 and the first loop 63 and the second loop 65 and the firstflexible compensating member or flexible link 67 and the second flexiblecompensating member or flexible link 71 are disposed so that as thestent is expanded the distance between the first flexible compensatingmember or flexible link 67 and the second flexible compensating memberor flexible link 71 increases and the longitudinal component of thefirst member 51, second member 54, third member 57 and fourth member 60decreases while the first loop 63 and the second loop 65 remaingenerally opposite to one another, the ends 68 and 69 of the firstflexible compensating member or flexible link 67 and the ends 72 and 73of the second flexible compensating member or flexible link 71 open soas to increase the variable longitudinal distance 70 between the firstend 68 and the second end 69 of the first flexible compensating memberor flexible link 67 and so as to increase the variable longitudinaldistance 74 between the first end 72 and the second end 73 of the secondflexible compensating member or flexible link 71. This compensates forthe decreasing of the longitudinal component of the first member 51,second member 54, third member 57, and fourth member 60 andsubstantially lessens the foreshortening of the stent upon itsexpansion. Upon expansion, the first flexible compensating member 67 andthe second flexible compensating member 71 impart support to the lumenbeing treated.

[0056]FIG. 15 shows the dimensions of an especially preferred embodimentof this invention. The deflection points, i.e., the first and secondloops 63 and 65 and the first and second compensating members 67 and 71,are made wider than the first, second, third, and fourth members 51, 54,57 and 60 so that the force of the deflection is distributed over awider area upon the expansion of the stent. The deflection points can bemade wider than the first, second, third and fourth members in differingamounts so that the deflection will occur in the narrower areas firstdue to the decreased resistance. In a preferred embodiment, the firstand second compensating members are wider than the first, second, thirdand fourth members and the first and second loops are wider than thefirst and second compensating members. One of the advantages of sizingthe first and second loops so that they are wider than the first andsecond compensating members is that the stent will substantiallycompensate for foreshortening as the stent is expanded. In theembodiment shown in FIG. 15, the first, second, third and fourth members51, 54, 57 and 60 have a width of about 0.1 mm. The first and secondloops 63 and 65 have a width of about 0.14 mm. The first and secondcompensating members 67 and 71 are provided with a thickened portion 75and 76 having a width of about 0.12 mm. Thus, in this especiallypreferred embodiment, the first and second loops have a width that isabout 40% greater and the first and second compensating members have awidth that is about 20% greater than the width of the first, second,third and fourth members.

[0057]FIGS. 16 through 20 show details of a stent constructed inaccordance with this invention.

[0058] Yet another advantage of Applicant's invention is shown in FIGS.21 to 24. For the sake of clarity, the dimensions and the degree ofdisplacement of the components of the stents shown in FIGS. 21 to 24 hasbeen intentionally exaggerated.

[0059]FIG. 21 is a cross-sectional front view taken along line A-A ofthe unexpanded stent made in accordance with applicants invention shownin FIG. 20. The unexpanded stent 200 of FIG. 21 is shown disposed in thelumen 202 of a blood vessel 201 prior to expansion. As previouslydiscussed, this stent is made by first cutting the stent pattern into aflat piece of sheet metal and then rolling the sheet metal into a tubeto form the tubular stent. As shown in FIG. 21 after rolling, the firstand second flexible compensating members 67 and 71 of the unexpandedstent tend to “flare out” in a direction away from the longitudinal axisor lumen of the stent. Thus, the flexible compensating members 67 and 71define outer diameters which are larger than the outer diameters definedby the remaining portions of the stent. FIG. 22 shows the stent of FIG.21 after it has been expanded in the lumen and against the internal wallof the blood vessel. As shown in FIG. 22, upon expansion of theunexpanded stent toward the wall of the blood vessels, the walls of theblood vessel imparts a mechanical force to the first and second flexiblecompensating members 67 and 71 and the compensating members move towardthe longitudinal axis or lumen of the stent until they are substantiallyin registry with the remaining portion of the stent. Thus, the lumen ofthe expanded stent is substantially circular when viewed in crosssection with substantially no portion of the expanded stent projectinginto the lumen or towards the longitudinal axis of the expanded stent.

[0060]FIG. 23 is similar to FIG. 21 except that the pattern has been cutinto a tubular member using conventional methods of making stents. Asshown in FIG. 23, the flexible compensating members do not flare outaway from the longitudinal axis of the unexpanded stent 203. Upon theexpansion of the stent shown in FIG. 23 toward the walls of the bloodvessel 201, the flexible compensating members 67′ and 71′ tend to “flarein” and project into the lumen 204 of the expanded stent 203.

[0061]FIG. 24 shows the stent 203 of FIG. 23 after it has been expandedin a lumen 204 of a blood vessel 201. The flexible compensating members67′ and 71′ are not in registry with the remaining portions of the stentand define a diameter smaller than the diameter of remaining portions ofthe stent. These projections into the lumen of the stent createturbulence in a fluid flowing through the longitudinal axis of theexpanded stent and could result in clot formation.

[0062] It will be appreciated by persons skilled in the art that thepresent invention is not limited to what has been particularly shown anddescribed hereinabove. Rather the scope of the present invention isdefined only by the claims which follow.

1. A method of fabricating a stent comprising the steps of: a) cutting aplurality of stent patterns into a flat piece of metal, each of saidpatterns having a first long side and a second long side, said firstlong side provided with a plurality of pairs of engagement troughs, saidsecond long side provided with a plurality of pairs of engagementprotrusions, said plurality of pairs of engagement troughs and saidplurality of pairs of engagement protrusions disposed substantiallyopposite each other, each of said plurality of pairs of said engagementtroughs comprising a first engagement trough and a second engagementtrough, said engagement troughs sized and disposed to receive and engagesaid engagement protrusions when said pattern is deformed and rolledinto a tubular shape, each pair of said engagement troughs provided witha bridge disposed between said first engagement trough and said secondengagement trough; b) providing said flat metal sheet with a pluralityof alignment apertures; c) deforming said pattern into a tubular shapeso that said pairs of engagement troughs engage said pairs of engagementprotrusions; d) cutting said bridge; and e) attaching each of saidengagement troughs to the engagement protrusion with which it isengaged, to form said expandable stent.
 2. The method of claim 1,further comprising the step of providing said sheet with a plurality ofalignment apertures.
 3. The method of claim 1, wherein step d) iscarried out using a laser.
 4. The method of claim 1, wherein step e) iscarried out utilizing a weld.
 5. The method of claim 4, wherein step e)is carried out using a welding run that is offset from the point wheresaid engagement troughs and said engagement protrusions contact eachother.
 6. The method of claim 5, wherein said welding run is offsetabout 0.01 mm from the point where said engagement troughs and saidengagement protrusions contact each other.
 7. The method of claim 4,wherein said weld is a spot weld.
 8. The method of claim 7, wherein aplurality of spot welds is utilized.
 9. The method of claim 8, wherein 5spot welds are utilized.
 10. The method of claim 1, wherein step e) iscarried out utilizing an adhesive.
 11. The method of claim 1, whereinstep e) is carried out utilizing a nail-like element.
 12. A method offabricating a stent comprising the steps of: a) cutting a plurality ofstent patterns into a flat piece of metal, each of said patternscomprising a plurality of flexible connected cells, each of saidflexible cells comprising: a) a first member having a longitudinalcomponent having a first end and a second end; b) a second member havinga longitudinal component having a first end and a second end, c) a thirdmember having a longitudinal component having a first end and a secondend; d) a fourth member having a longitudinal component having a firstend and a second end; e) a first loop defining a first angle disposedbetween said first end of said first member and said first end of saidsecond member; f) a second loop defining a second angle disposed betweensaid second end of said third member and said second end of said fourthmember, and disposed generally opposite to said first loop; g) a firstflexible compensating member or flexible link having a first end and asecond end disposed between said first member and said third member,said first end of said first flexible compensating member or flexiblelink communicating with said second end of said first member and saidsecond end of said first flexible compensating member or flexible linkcommunicating with said first end of said third member, said first andsaid second ends disposed a variable longitudinal distance from eachother; h) a second flexible compensating member or flexible link havinga first end and a second end disposed between said second member andsaid fourth member, said first end of said second flexible compensatingmember or flexible link communicating with said second end of saidsecond member and said second end of said second flexible compensatingmember or flexible link communicating with said first end of said fourthmember, said first and said second ends disposed a variable longitudinaldistance from each other, said first and said second flexiblecompensating member or flexible links differentially extendable orcompressible when said stent is bent in a curved direction away from thelongitudinal axis of said aperture; and i) said first, said second, saidthird, and said fourth members and said first and said second loops, andsaid first and said second flexible compensating member or flexiblelinks disposed so that as said stent is expanded the distance betweensaid first and said second flexible compensating member or flexiblelinks increases and the longitudinal component of said first, second,third and fourth members decreases while said first and said secondloops remain generally opposite to one another, the ends of said firstand said second flexible compensating member or flexible links open soas to increase said variable longitudinal distance between said firstand said second ends of said first flexible compensating member orflexible link and so as to increase said variable longitudinal distancebetween said first and said second ends of said second flexiblecompensating member or flexible link so as to compensate for thedecreasing of the longitudinal component of said first, second, third,and fourth members and substantially lessen the foreshortening of saidstent upon its expansion; each of said plurality of stent patternshaving a first long side and a second long side, said first long sideprovided with a plurality of pairs of engagement troughs, said secondlong side provided with a plurality of pairs of engagement protrusions,said plurality of pairs of engagement troughs and said plurality ofpairs of engagement protrusions disposed substantially opposite eachother, each of said plurality of pairs of said engagement troughscomprising a first engagement trough and a second engagement trough,said engagement troughs sized and disposed to receive and engage saidengagement protrusions when said pattern is deformed and rolled into atubular shape, each pair of said engagement troughs provided with abridge disposed between said first engagement trough and said secondengagement trough; b) deforming said pattern into a tubular shape sothat said pairs of engagement troughs engage said pairs of engagementprotrusions; c) cutting said bridge; and d) attaching each of saidengagement troughs to the engagement protrusion with which it isengaged, to form said expandable stent.
 13. The method of claim 12,further comprising the step of providing said flat metal sheet with aplurality of alignment apertures.
 14. The method of claim 12, whereinsaid first loop, said second loop, said first compensating member, andsaid second compensating member are wider than said first, second, thirdand fourth members.
 15. The method of claim 14, wherein said first andsaid second compensating members are wider than said first, second,third, and fourth members and said first and said second loops are widerthan said first and said second compensating members.
 16. The method ofclaim 15, wherein said first and said second loops have a width that isabout 40% greater than the width of said first, second, third, andfourth members and said first and said second compensating members havea width that is about 20% greater than the width of said first, second,third, and fourth members.
 17. The method of claim 12, wherein step c)is carried out using a laser.
 18. The method of claim 12, wherein stepd) is carried out utilizing a weld.
 19. The method of claim 18, whereinstep d) is carried out utilizing a welding run that is offset from thepoint where said engagement troughs and said engagement protrusionscontact each other.
 20. The method of claim 19, wherein said welding runis offset about 0.01 mm from the point where said engagement troughs andsaid engagement protrusions contact each other.
 21. The method of claim18, wherein said weld is a spot weld.
 22. The method of claim 21,wherein a plurality of spot welds is utilized.
 23. The method of claim22, wherein 5 spot welds are utilized.
 24. The method of claim 12,wherein step d) is carried out utilizing an adhesive.
 25. The method ofclaim 12, wherein step d) is carried out utilizing a nail-like element.26. A sheet for fabricating a stent having a longitudinal lumencomprising: a flat piece of metal provided with a plurality of stentpatterns, each of said patterns having a first long side and a secondlong side, said first long side provided with a plurality of pairs ofengagement troughs, said second long side provided with a plurality ofpairs of engagement protrusions, said plurality of pairs of engagementtroughs and said plurality of pairs of engagement protrusions disposedsubstantially opposite each other, each of said plurality of pairs ofsaid engagement troughs comprising a first engagement trough and asecond engagement trough, said engagement troughs sized and disposed toreceive and engage said engagement protrusions when said pattern isdeformed and rolled into a tubular shape, each pair of said engagementtroughs provided with a bridge disposed between said first engagementtrough and said second engagement trough.
 27. The sheet of claim 26,further comprising a plurality of alignment apertures disposed in saidsheet.
 28. A sheet for fabricating a stent having a longitudinal lumencomprising: a) a flat piece of metal provided with a plurality of stentpatterns, each of said patterns comprising a plurality of flexibleconnected cells, each of said flexible cells comprising: a) a firstmember having a longitudinal component having a first end and a secondend; b) a second member having a longitudinal component having a firstend and a second end, c) a third member having a longitudinal componenthaving a first end and a second end; d) a fourth member having alongitudinal component having a first end and a second end; e) a firstloop defining a first angle disposed between said first end of saidfirst member and said first end of said second member; f) a second loopdefining a second angle disposed between said second end of said thirdmember and said second end of said fourth member, and disposed generallyopposite to said first loop; g) a first flexible compensating member orflexible link having a first end and a second end disposed between saidfirst member and said third member, said first end of said firstflexible compensating member or flexible link communicating with saidsecond end of said first member and said second end of said firstflexible compensating member or flexible link communicating with saidfirst end of said third member, said first and said second ends disposeda variable longitudinal distance from each other; h) a second flexiblecompensating member or flexible link having a first end and a second enddisposed between said second member and said fourth member, said firstend of said second flexible compensating member or flexible linkcommunicating with said second end of said second member and said secondend of said second flexible compensating member or flexible linkcommunicating with said first end of said fourth member, said first andsaid second ends disposed a variable longitudinal distance from eachother, said first and said second flexible compensating member orflexible links differentially extendable or compressible when said stentis bent in a curved direction away from the longitudinal axis of saidaperture; and i) said first, said second, said third, and said fourthmembers and said first and said second loops, and said first and saidsecond flexible compensating member or flexible links disposed so thatas said stent is expanded the distance between said first and saidsecond flexible compensating member or flexible links increases and thelongitudinal component of said first, second, third and fourth membersdecreases while said first and said second loops remain generallyopposite to one another, the ends of said first and said second flexiblecompensating member or flexible links open so as to increase saidvariable longitudinal distance between said first and said second endsof said first flexible compensating member or flexible link and so as toincrease said variable longitudinal distance between said first and saidsecond ends of said second flexible compensating member or flexible linkso as to compensate for the decreasing of the longitudinal component ofsaid first, second, third, and fourth members and substantially lessenthe foreshortening of said stent upon its expansion; each of saidplurality of stent patterns having a first long side and a second longside, said first long side provided with a plurality of pairs ofengagement troughs, said second long side provided with a plurality ofpairs of engagement protrusions, said plurality of pairs of engagementtroughs and said plurality of pairs of engagement protrusions disposedsubstantially opposite each other, each of said plurality of pairs ofsaid engagement troughs comprising a first engagement trough and asecond engagement trough, said engagement troughs sized and disposed toreceive and engage said engagement protrusions when said pattern isdeformed and rolled into a tubular shape, each pair of said engagementtroughs provided with a bridge disposed between said first engagementtrough and said second engagement trough.
 29. The sheet of claim 28,further comprising a plurality of alignment apertures disposed in saidflat metal sheet.
 30. The sheet of claim 28, wherein said first loop,said second loop, said first compensating member, and said secondcompensating member are wider than said first, second, third and fourthmembers.
 31. The sheet of claim 30, wherein said first and said secondcompensating members are wider than said first, second, third, andfourth members and said first and said second loops are wider than saidfirst and said second compensating members.
 32. The sheet of claim 31,wherein said first and said second loops have a width that is about 40%greater than the width of said first, second, third, and fourth membersand said first and said second compensating members have a width that isabout 20% greater than the width of said first, second, third, andfourth members.
 33. An expandable stent having a longitudinal lumencomprising: a) a first long side and a second long side, said first longside provided with a plurality of pairs of engagement troughs, saidsecond long side provided with a plurality of pairs of engagementprotrusions, said plurality of pairs of engagement troughs and saidplurality of pairs of engagement protrusions disposed substantiallyopposite each other, said plurality of engagement troughs sized anddisposed to receive and engage said engagement protrusions, saidengagement troughs attached to said engagement protrusions.
 34. Thestent of claim 33, wherein said engagement troughs are attached to saidengagement protrusions by a weld.
 35. The stent of claim 34, whereinsaid weld is offset from the point where said engagement troughs andsaid engagement protrusions contact each other.
 36. The stent of claim35, wherein said weld is offset about 0.01 mm from the point where saidengagement troughs and said engagement protrusions contact each other.37. The stent of claim 34, wherein said weld is a spot weld.
 38. Thestent of claim 37, wherein a plurality of spot welds is utilized. 39.The stent of claim 38, wherein 5 spot welds are utilized.
 40. The stentof claim 33, wherein said engagement troughs are attached to saidengagement protrusions by an adhesive.
 41. The stent of claim 33,wherein said engagement troughs are attached to said engagementprotrusions by a nail-like element.
 42. An expandable stent having alongitudinal lumen comprising: a) a stent pattern comprising a pluralityof flexible connected cells, each of said flexible cells comprising: a)a first member having a longitudinal component having a first end and asecond end; b) a second member having a longitudinal component having afirst end and a second end, c) a third member having a longitudinalcomponent having a first end and a second end; d) a fourth member havinga longitudinal component having a first end and a second end; e) a firstloop defining a first angle disposed between said first end of saidfirst member and said first end of said second member; f) a second loopdefining a second angle disposed between said second end of said thirdmember and said second end of said fourth member, and disposed generallyopposite to said first loop; g) a first flexible compensating member orflexible link having a first end and a second end disposed between saidfirst member and said third member, said first end of said firstflexible compensating member or flexible link communicating with saidsecond end of said first member and said second end of said firstflexible compensating member or flexible link communicating with saidfirst end of said third member, said first and said second ends disposeda variable longitudinal distance from each other; h) a second flexiblecompensating member or flexible link having a first end and a second enddisposed between said second member and said fourth member, said firstend of said second flexible compensating member or flexible linkcommunicating with said second end of said second member and said secondend of said second flexible compensating member or flexible linkcommunicating with said first end of said fourth member, said first andsaid second ends disposed a variable longitudinal distance from eachother, said first and said second flexible compensating member orflexible links differentially extendable or compressible when said stentis bent in a curved direction away from the longitudinal axis of saidaperture; and i) said first, said second, said third, and said fourthmembers and said first and said second loops, and said first and saidsecond flexible compensating member or flexible links disposed so thatas said stent is expanded the distance between said first and saidsecond flexible compensating member or flexible links increases and thelongitudinal component of said first, second, third and fourth membersdecreases while said first and said second loops remain generallyopposite to one another, the ends of said first and said second flexiblecompensating member or flexible links open so as to increase saidvariable longitudinal distance between said first and said second endsof said first flexible compensating member or flexible link and so as toincrease said variable longitudinal distance between said first and saidsecond ends of said second flexible compensating member or flexible linkso as to compensate for the decreasing of the longitudinal component ofsaid first, second, third, and fourth members and substantially lessenthe foreshortening of said stent upon its expansion; said stent patternhaving a first long side and a second long side, said first long sideprovided with a plurality of pairs of engagement troughs, said secondlong side provided with a plurality of pairs of engagement protrusions,said plurality of pairs of engagement troughs and said plurality ofpairs of engagement protrusions disposed substantially opposite eachother, each of said plurality of pairs of said engagement troughscomprising a first engagement trough and a second engagement trough,said engagement troughs attached to said engagement protrusions.
 43. Thestent of claim 42, wherein said first loop, said second loop, said firstcompensating member, and said second compensating member are wider thansaid first, second, third and fourth members.
 44. The stent of claim 43,wherein said first and said second compensating members are wider thansaid first, second, third, and fourth members and said first and saidsecond loops are wider than said first and said second compensatingmembers.
 45. The stent of claim 44, wherein said first and said secondloops have a width that is about 40% greater than the width of saidfirst, second, third, and fourth members and said first and said secondcompensating members have a width that is about 20% greater than thewidth of said first, second, third, and fourth members.
 46. The stent ofclaim 42, wherein said engagement protrusions are attached to saidengagement troughs by a weld.
 47. The stent of claim 46, wherein saidweld is offset from the point where said engagement troughs and saidengagement protrusions contact each other.
 48. The stent of claim 47,wherein said weld is offset about 0.01 mm from the point where saidengagement troughs and said engagement protrusions contact each other.49. The stent of claim 46, wherein said weld is a spot weld.
 50. Thestent of claim 49, wherein a plurality of spot welds is utilized. 51.The stent of claim 50, wherein 5 spot welds are utilized.
 52. The stentof claim 42, wherein said engagement protrusions are attached to saidengagement troughs via an adhesive.
 53. The stent of claim 42, whereinsaid engagement protrusions are attached to said engagement troughs by anail-like element.
 54. The method of claim 1, said stent defining alongitudinal lumen wherein substantially no portion of said stentprojects into said longitudinal lumen upon expansion of said stentagainst the internal wall of a vessel.
 55. The method of claim 12, saidstent defining a longitudinal lumen wherein substantially no portion ofsaid stent projects into said longitudinal lumen upon expansion of saidstent against the internal wall of a vessel.
 56. The sheet of claim 26,said stent patterns adapted so that upon expansion of said stentsubstantially no portion of said stent protrudes into the longitudinallumen of said stent against the internal wall of a vessel.
 57. The sheetof claim 28, said stent patterns adapted so that upon expansion of saidstent against the internal wall of a vessel substantially no portion ofsaid stent protrudes into the longitudinal lumen of said stent.
 58. Thestent of claim 33, said stent adapted that upon expansion of said stentagainst the internal wall of a vessel substantially no portion of saidstent projects into said lumen.
 59. The stent of claim 42, said stentpatterns adapted so that upon expansion of said stent against theinternal wall of a vessel substantially no-portion of said stentprotrudes into said longitudinal lumen of said stent.
 60. An expandablestent having a longitudinal lumen, comprising: A plurality of portionsconnecting by a plurality of flexible compensating members, saidflexible compensating members projecting from the external surface ofsaid stent when said stent is unexpanded and said flexible connectingmembers substantially in registry with the remaining portions of saidstent and said stent is expanded against the internal walls of a bloodvessel.
 61. The stent of claim 60, wherein said stent is formed from asubstantially flat sheet.
 62. An expandable stent having a longitudinallumen, comprising: A plurality of portions connected by a plurality offlexible compensating members wherein substantially no portion of saidstent projects into said lumen when said stent is expanded against theinternal wall of a blood vessel.
 63. The stent of claim 62 wherein saidstent is formed from a substantially flat sheet.